US4796095A - Method of generating image scanning clock signals in optical scanning apparatus - Google Patents
Method of generating image scanning clock signals in optical scanning apparatus Download PDFInfo
- Publication number
- US4796095A US4796095A US07/099,539 US9953987A US4796095A US 4796095 A US4796095 A US 4796095A US 9953987 A US9953987 A US 9953987A US 4796095 A US4796095 A US 4796095A
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- Prior art keywords
- clock signals
- signals
- image scanning
- phase
- scanning
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
- H04N1/04—Scanning arrangements, i.e. arrangements for the displacement of active reading or reproducing elements relative to the original or reproducing medium, or vice versa
- H04N1/047—Detection, control or error compensation of scanning velocity or position
- H04N1/053—Detection, control or error compensation of scanning velocity or position in main scanning direction, e.g. synchronisation of line start or picture elements in a line
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N2201/00—Indexing scheme relating to scanning, transmission or reproduction of documents or the like, and to details thereof
- H04N2201/024—Indexing scheme relating to scanning, transmission or reproduction of documents or the like, and to details thereof deleted
- H04N2201/02406—Arrangements for positioning elements within a head
- H04N2201/02439—Positioning method
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N2201/00—Indexing scheme relating to scanning, transmission or reproduction of documents or the like, and to details thereof
- H04N2201/04—Scanning arrangements
- H04N2201/047—Detection, control or error compensation of scanning velocity or position
- H04N2201/04701—Detection of scanning velocity or position
- H04N2201/0471—Detection of scanning velocity or position using dedicated detectors
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N2201/00—Indexing scheme relating to scanning, transmission or reproduction of documents or the like, and to details thereof
- H04N2201/04—Scanning arrangements
- H04N2201/047—Detection, control or error compensation of scanning velocity or position
- H04N2201/04701—Detection of scanning velocity or position
- H04N2201/04732—Detecting at infrequent intervals, e.g. once or twice per line for main-scan control
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N2201/00—Indexing scheme relating to scanning, transmission or reproduction of documents or the like, and to details thereof
- H04N2201/04—Scanning arrangements
- H04N2201/047—Detection, control or error compensation of scanning velocity or position
- H04N2201/04701—Detection of scanning velocity or position
- H04N2201/04744—Detection of scanning velocity or position by detecting the scanned beam or a reference beam
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N2201/00—Indexing scheme relating to scanning, transmission or reproduction of documents or the like, and to details thereof
- H04N2201/04—Scanning arrangements
- H04N2201/047—Detection, control or error compensation of scanning velocity or position
- H04N2201/04753—Control or error compensation of scanning position or velocity
- H04N2201/04758—Control or error compensation of scanning position or velocity by controlling the position of the scanned image area
- H04N2201/04767—Control or error compensation of scanning position or velocity by controlling the position of the scanned image area by controlling the timing of the signals, e.g. by controlling the frequency o phase of the pixel clock
- H04N2201/04781—Controlling the phase of the signals
- H04N2201/04784—Controlling the phase of the signals using one or more clock signals selected from a number of clock signals of different phases
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N2201/00—Indexing scheme relating to scanning, transmission or reproduction of documents or the like, and to details thereof
- H04N2201/04—Scanning arrangements
- H04N2201/047—Detection, control or error compensation of scanning velocity or position
- H04N2201/04753—Control or error compensation of scanning position or velocity
- H04N2201/04794—Varying the control or compensation during the scan, e.g. using continuous feedback or from line to line
Definitions
- the present invention relates to a method of generating image scanning clock signals in an optical scanning apparatus.
- optical scanning apparatus in which a light beam is periodically deflected by a rotating light beam deflector such as a rotating polygonal mirror or a hologram grating disk for reading or writing information.
- a rotating light beam deflector such as a rotating polygonal mirror or a hologram grating disk for reading or writing information.
- the light beam such as a laser beam
- the rotating light beam deflector into a scanning beam which is focused as a spot on and scans a surface through a suitable optical system.
- the surface being scanned may be an original having information if such information is to be read, or may be a photoconductive photosensitive body when information is to be written. While the scanning beam is scanning the surface, the information is read or written at the rate of one pixel per one clock pulse in response to image scanning clock signals.
- main scanning The scanning of an object surface with a scanning beam is known as "main scanning".
- main scanning the object surface is fed in a direction normal to the direction in which the main scanning occurs.
- auxiliary scanning The feeding of the object surface is called as "auxiliary scanning”.
- One way of synchronizing the main scanning cycles is to use image scanning clock signals. According to this process, the instant the light sensor detects the scanning beam, image scanning clock pulses start being counted by m, and a main scanning cycle is started when (m+1) pulses are counted.
- the image scanning clock signals are successively generated. Since the interval between output signals from the light sensor, which serve as a reference for synchronization of main scanning cycles, varies due for example to the mechanical accuracy of the rotating light beam deflector, the time interval from detection by the light sensor of the scanning beam to the starting of a main scanning cycle varies up to one clock pulse at maximum dependent on whether the light sensor output signals are generated upon high or low levels of the clock signals, resulting in scanning irregularities.
- Variations in the time interval from detection by the light sensor of the scanning beam to the starting of a main scanning cycle up to one clock pulse at maximum mean that the positions of the main scanning starting points vary up to one pixel.
- n pulse signals C 1 through Cn are produced by a shift register from reference clock signals of the same frequency as that of image scanning clock signals, the pulse signals C 1 through C n being successively shifted in phase by a constant phase difference such that the phase difference between the pulse signals C 1 and C n are smaller than one period of the image scanning clock signals, and one of the pulse signals C 1 through C n is selected as an image scanning clock signal.
- the method of generating image scanning clock signals according to the present invention can be carried out by an optical scanning apparatus in which a light beam is deflected by a rotating light beam deflector such as a rotating polygonal mirror or a hologram grating disk to scan a surface area, and the light beam is detected by a light sensor disposed outside of the surface area being scanned for synchronizing main scanning cycles.
- a rotating light beam deflector such as a rotating polygonal mirror or a hologram grating disk
- One of a plurality of pulse signal groups which are of the same frequency as that of image scanning clock signals and are shifted in phase from each other is selected as image scanning clock signals by an output signal from the light sensor.
- Reference clock signals C 0 of the same frequency as that of the image scanning clock signals are applied to a shift register.
- Corrective clock signals SCK of a higher frequency than that of the reference clock signals C 0 are applied as shift clock signals to the shift register.
- the shift register generates n output signals C 1 , C 2 , . . . C n (n ⁇ 2) which are successively delayed a phase ⁇ t by delay circuits to produce the aforesaid plurality of pulse signal groups.
- the reference clock signals are accurately successively shifted a certain phase by the shift register and then shifted ⁇ t by the delay circuits. Therefore, the shift clock signals for the shift register are not required to be of an extremely high frequency, and positional variations of main scanning starting points are reduced. For example, where the frequency of image scanning clock signals is 10 MHz to make positional variations of the main scanning starting points smaller than 1/10 pixel, the frequency of shift clock signals may be lower than 100 MHz.
- FIG. 1 is a block diagram of a circuit arrangement for carrying out a method according to the present invention
- FIGS. 2 through 4 are timing charts explaining the method of the invention.
- FIG. 5 is a block diagram of a clock selector circuit in the circuit arrangement shown in FIG. 1.
- reference clock signals C 0 are generated by a reference clock oscillator 10 and applied to shift registers 14, 16.
- the reference clock signals C 0 are of the same frequency as that of image scanning clock signals, i.e., f 0 MHz.
- the shift register 14 is supplied with the corrective clock signals SCK1 as shift clocks and produce output signals C 1 , C 3 , . . . C n-1 which are generated by shifting the reference clock signals C 0 in phase by one clock signal of the corrective clock signals SCK1.
- the shift register 16 is supplied with the corrective clock signals SCK2 as shift clocks and produce output signals C 2 , C 4 , C 6 , . . . , C n which are generated by shifting the reference clock signals C 0 in phase by one clock signal of the corrective clock signals SCK2.
- n pulse signals C 1 through C n are produced which are of the same frequency f 0 as that of the reference clock signals and shifted in phase by one clock signal of the corrective clock signals SCK1, with n being an even number. If n is an odd number, the shift register 14 generates output signals C 1 , C 3 , C 5 , . . . C n , and the shift register 14 generates output signals C 2 , C 4 , . . . C n-1 .
- n is regarded as an even number.
- FIG. 2 clearly indicates that the output signals C 1 through C n from the shift registers 14, 16 are shifted in phase by 1/n dot with accuracy.
- the output signals from the shift register 14 are applied respectively to n/2 delay circuits 18-1, 18-3, 18-5, . . . 18-n-1 in one-to-one correspondence, and the output signals from the shift register 16 are applied respectively to n/2 delay circuits 18-2, 18-4, . . . 18-n in one-to-one correspondence.
- n ⁇ k pulse signal groups C 1-1 , C 1-2 , . . . C 1-k , C 2-k , . . . C n-1 , . . . C n-k are obtained.
- These signal groups are mutually shifted ⁇ t in phase
- FIG. 3 shows these pulse signal groups. Denoted at ⁇ t 0 in FIG. 3 is the one-clock-signal interval of the corrective clock signals SCK. Naturally, 0 ⁇ t ⁇ (1/n ⁇ f 0 ).
- the n ⁇ k pulse signal groups C 1-1 , C 1-2 , . . . C n-k are applied to a latch circuit 20 which is also supplied with a synchronism detecting signal.
- the latch circuit 20 latches the n ⁇ k input signals C 1-1 , C 1-2 , . . . C n-k and produces 2nk output signals Q 1 , Q 1 , Q 2 , Q 2 , . . . Q k , Q k , . . . Q nk , Q nk .
- the synchronism detecting signal is produced by a light sensor disposed outside of a main scanning region near main scanning starting points when the light sensor detects a scanning beam.
- the clock selector circuit 22 selects one of the pulse signal groups C l-1 through C n-k and issues the selected pulse signal group as image scanning clock signals.
- the image scanning clock signals are counted by a counter (not shown). When a prescribed number of clock pulses are counted, a main scanning cycle for scanning a surface with a scanning beam is started.
- FIG. 4 is a timing chart where C 2-2 is selected from six pulse signal groups as image scanning clock signals.
- pulse signal groups C l-1 through C 3-2 and the synchronism detecting signal being of the relationship as shown in FIG. 4, the pulse signal groups C 1-1 , C 3-1 , C 3-2 as latched by the latch circuit 20 in response to the leading edge of the synchronism detecting signal are high and the pulse signal groups C 1-2 , C 2-1 , C 2-2 as latched by the latch circuit 20 in response to the leading edge of the synchronism detecting signal are low.
- the output signals Q 1 , Q 1 of the latch circuit 12 correspond to C 1-1 , the output signals Q 2 , Q 2 to C 1-2 , the output signals Q 3 , Q 3 - to C 2-1 , the output signals Q 4 , Q 4 to C 2-2 , the output signals Q 5 , Q 5 to C 3-1 , and the output signals Q 6 , Q 6 to C 3-2 .
- j is a design parameter which can appropriately be selected.
- the condition immediately before the image scanning clock signals are selected by the sychronism detecting signal is undefined in FIG. 4. Stated otherwise, switching from the image scanning clock signals before selection is made by the synchronism detecting signal to the presently selected image scanning clock signals is effected.
- the condition immediately before image scanning clock signals are selected is a certain defined condition.
- ⁇ t is established to meet the following relationships: (A) where ##EQU3##
Abstract
Description
TABLE ______________________________________ i Qi .sup.--Qi Qi .sup.--Qi + 1 ______________________________________ 1 1 0 1 2 0 1 0 3 0 1 0 4 0 1 0 5 1 0 0 6 1 0 0 ______________________________________
Claims (2)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP61-226641 | 1986-09-09 | ||
JP22664186 | 1986-09-09 |
Publications (1)
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US4796095A true US4796095A (en) | 1989-01-03 |
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US07/099,539 Expired - Lifetime US4796095A (en) | 1986-09-09 | 1987-09-22 | Method of generating image scanning clock signals in optical scanning apparatus |
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Cited By (24)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4907089A (en) * | 1988-01-14 | 1990-03-06 | Sony Corp. | Timing pulse generator |
US4916388A (en) * | 1988-04-01 | 1990-04-10 | Nec Corporation | Semiconductor integrated circuit device equipped with scan-pass type test circuit |
US4970405A (en) * | 1987-12-11 | 1990-11-13 | Nec Corporation | Clock selection circuit for selecting one of a plurality of clock pulse signals |
US5015871A (en) * | 1989-11-03 | 1991-05-14 | Harris Corporation | Multiple external asynchronous triggers circuit |
US5045951A (en) * | 1988-09-02 | 1991-09-03 | Hitachi, Ltd. | Video signal processor and video signal processing method for a video printer |
US5187725A (en) * | 1990-06-28 | 1993-02-16 | Canon Kabushiki Kaisha | Data detector at output of counter |
EP0531166A1 (en) * | 1991-09-06 | 1993-03-10 | Xerox Corporation | Seam-less data recovery |
US5220201A (en) * | 1990-06-26 | 1993-06-15 | Canon Kabushiki Kaisha | Phase-locked signal generator |
US5287025A (en) * | 1991-04-23 | 1994-02-15 | Matsushita Electric Industrial Co., Ltd. | Timing control circuit |
US5331342A (en) * | 1991-03-12 | 1994-07-19 | Mita Industrial Co., Ltd. | Video clock generating circuit and horizontal synchronizing signal generating device in image forming apparatus using laser beam |
US5371417A (en) * | 1993-07-02 | 1994-12-06 | Tandem Computers Incorporated | Multiple frequency output clock generator system |
US5438353A (en) * | 1992-11-02 | 1995-08-01 | Hewlett-Packard Company | Clock signal generator for electrophotographic printers |
US5457487A (en) * | 1992-01-08 | 1995-10-10 | Canon Kabushiki Kaisha | Color image forming apparatus which times release of each of plural color image signals |
US5477330A (en) * | 1992-10-16 | 1995-12-19 | Printware, Inc. | Synchronization to a start-of-scan detection, and digital generation of variable frequencies, from a fixed-frequency fixed-phase frequency source in an image generator in order to highly accurately time the placement of pixels upon a scan line |
US5534808A (en) * | 1992-01-31 | 1996-07-09 | Konica Corporation | Signal delay method, signal delay device and circuit for use in the apparatus |
US5550514A (en) * | 1993-04-28 | 1996-08-27 | Telefonaktiebolaget Lm Ericsson | Digital controlled xtal osc |
US5589788A (en) * | 1994-05-12 | 1996-12-31 | Hewlett-Packard Company | Timing adjustment circuit |
US5729664A (en) * | 1994-08-12 | 1998-03-17 | Fuji Xerox Co., Ltd. | Image processing apparatus and method for converting an input color image signal from one color space to another |
US5982408A (en) * | 1997-04-10 | 1999-11-09 | Lexmark International, Inc. | Method and apparatus for HSYNC synchronization |
US20030137330A1 (en) * | 2002-01-18 | 2003-07-24 | Minobu Yazawa | Semiconductor device with delay correction function |
US20040207890A1 (en) * | 2003-04-16 | 2004-10-21 | Breswick Curt Paul | Method and apparatus for controlling shifting of data out of at least one image sensor |
US20050219354A1 (en) * | 2004-02-23 | 2005-10-06 | Atsufumi Omori | Pixel clock generator, optical scanner, and image forming apparatus |
USRE42555E1 (en) | 1999-09-01 | 2011-07-19 | Faust Communications, Llc | Merged pipeline for color interpolation and edge enhancement of digital images |
USRE43357E1 (en) | 1999-09-01 | 2012-05-08 | Faust Communications, Llc | Color interpolator and horizontal/vertical edge enhancer using two line buffer and alternating even/odd filters for digital camera |
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US4268867A (en) * | 1979-06-29 | 1981-05-19 | Xerox Corporation | Pixel clock for scanner |
US4443765A (en) * | 1981-09-18 | 1984-04-17 | The United States Of America As Represented By The Secretary Of The Navy | Digital multi-tapped delay line with automatic time-domain programming |
US4638497A (en) * | 1983-09-26 | 1987-01-20 | Hitachi, Ltd. | Framing code detector for a teletext receiver |
US4713621A (en) * | 1984-03-29 | 1987-12-15 | Fujitsu Limited | Phase synchronization circuit |
-
1987
- 1987-09-22 US US07/099,539 patent/US4796095A/en not_active Expired - Lifetime
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US4000368A (en) * | 1975-08-04 | 1976-12-28 | Dacom, Inc. | Nonuniform clock generator for document reproduction apparatus |
US4268867A (en) * | 1979-06-29 | 1981-05-19 | Xerox Corporation | Pixel clock for scanner |
US4443765A (en) * | 1981-09-18 | 1984-04-17 | The United States Of America As Represented By The Secretary Of The Navy | Digital multi-tapped delay line with automatic time-domain programming |
US4638497A (en) * | 1983-09-26 | 1987-01-20 | Hitachi, Ltd. | Framing code detector for a teletext receiver |
US4713621A (en) * | 1984-03-29 | 1987-12-15 | Fujitsu Limited | Phase synchronization circuit |
Cited By (29)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4970405A (en) * | 1987-12-11 | 1990-11-13 | Nec Corporation | Clock selection circuit for selecting one of a plurality of clock pulse signals |
US4907089A (en) * | 1988-01-14 | 1990-03-06 | Sony Corp. | Timing pulse generator |
US4916388A (en) * | 1988-04-01 | 1990-04-10 | Nec Corporation | Semiconductor integrated circuit device equipped with scan-pass type test circuit |
US5045951A (en) * | 1988-09-02 | 1991-09-03 | Hitachi, Ltd. | Video signal processor and video signal processing method for a video printer |
US5015871A (en) * | 1989-11-03 | 1991-05-14 | Harris Corporation | Multiple external asynchronous triggers circuit |
US5220201A (en) * | 1990-06-26 | 1993-06-15 | Canon Kabushiki Kaisha | Phase-locked signal generator |
US5187725A (en) * | 1990-06-28 | 1993-02-16 | Canon Kabushiki Kaisha | Data detector at output of counter |
US5331342A (en) * | 1991-03-12 | 1994-07-19 | Mita Industrial Co., Ltd. | Video clock generating circuit and horizontal synchronizing signal generating device in image forming apparatus using laser beam |
US5287025A (en) * | 1991-04-23 | 1994-02-15 | Matsushita Electric Industrial Co., Ltd. | Timing control circuit |
EP0531166A1 (en) * | 1991-09-06 | 1993-03-10 | Xerox Corporation | Seam-less data recovery |
US5457487A (en) * | 1992-01-08 | 1995-10-10 | Canon Kabushiki Kaisha | Color image forming apparatus which times release of each of plural color image signals |
US5686850A (en) * | 1992-01-31 | 1997-11-11 | Konica Corporation | Signal delay method, signal delay device and circuit for use in the apparatus |
US5534808A (en) * | 1992-01-31 | 1996-07-09 | Konica Corporation | Signal delay method, signal delay device and circuit for use in the apparatus |
US5477330A (en) * | 1992-10-16 | 1995-12-19 | Printware, Inc. | Synchronization to a start-of-scan detection, and digital generation of variable frequencies, from a fixed-frequency fixed-phase frequency source in an image generator in order to highly accurately time the placement of pixels upon a scan line |
US5438353A (en) * | 1992-11-02 | 1995-08-01 | Hewlett-Packard Company | Clock signal generator for electrophotographic printers |
US5550514A (en) * | 1993-04-28 | 1996-08-27 | Telefonaktiebolaget Lm Ericsson | Digital controlled xtal osc |
US5461332A (en) * | 1993-07-02 | 1995-10-24 | Tandem Computers Incorporated | Multiple frequency output clock generator system |
US5491442A (en) * | 1993-07-02 | 1996-02-13 | Tandem Computers Incorporated | Multiple frequency output clock generator system |
US5371417A (en) * | 1993-07-02 | 1994-12-06 | Tandem Computers Incorporated | Multiple frequency output clock generator system |
US5589788A (en) * | 1994-05-12 | 1996-12-31 | Hewlett-Packard Company | Timing adjustment circuit |
US5729664A (en) * | 1994-08-12 | 1998-03-17 | Fuji Xerox Co., Ltd. | Image processing apparatus and method for converting an input color image signal from one color space to another |
US5982408A (en) * | 1997-04-10 | 1999-11-09 | Lexmark International, Inc. | Method and apparatus for HSYNC synchronization |
USRE42555E1 (en) | 1999-09-01 | 2011-07-19 | Faust Communications, Llc | Merged pipeline for color interpolation and edge enhancement of digital images |
USRE43357E1 (en) | 1999-09-01 | 2012-05-08 | Faust Communications, Llc | Color interpolator and horizontal/vertical edge enhancer using two line buffer and alternating even/odd filters for digital camera |
US20030137330A1 (en) * | 2002-01-18 | 2003-07-24 | Minobu Yazawa | Semiconductor device with delay correction function |
US6720811B2 (en) * | 2002-01-18 | 2004-04-13 | Renesas Technology Corp. | Semiconductor device with delay correction function |
US20040207890A1 (en) * | 2003-04-16 | 2004-10-21 | Breswick Curt Paul | Method and apparatus for controlling shifting of data out of at least one image sensor |
US20050219354A1 (en) * | 2004-02-23 | 2005-10-06 | Atsufumi Omori | Pixel clock generator, optical scanner, and image forming apparatus |
US8005321B2 (en) * | 2004-02-23 | 2011-08-23 | Ricoh Company, Limited | Pixel clock generator, optical scanner, and image forming apparatus |
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